selftests/bpf: Add libbpf_probe_bpf_kfunc API selftests

Add selftests for prog_kfunc feature probing.

 ./test_progs -t libbpf_probe_kfuncs
 #153     libbpf_probe_kfuncs:OK
 Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Tao Chen <[email protected]>

Author: chentao-kernel

tools/testing/selftests/bpf/prog_tests/libbpf_probes.c

@@ -126,3 +126,121 @@ void test_libbpf_probe_helpers(void)
 		ASSERT_EQ(res, d->supported, buf);
 	}
 }
+
+static int module_btf_fd(char *module)
+{
+	int fd, err;
+	__u32 id = 0, len;
+	struct bpf_btf_info info;
+	char name[64];
+
+	while (true) {
+		err = bpf_btf_get_next_id(id, &id);
+		if (err && (errno == ENOENT || errno == EPERM))
+			return 0;
+		if (err) {
+			err = -errno;
+			return err;
+		}
+		fd = bpf_btf_get_fd_by_id(id);
+		if (fd < 0) {
+			if (errno == ENOENT)
+				continue;
+			err = -errno;
+			return err;
+		}
+		len = sizeof(info);
+		memset(&info, 0, sizeof(info));
+		info.name = ptr_to_u64(name);
+		info.name_len = sizeof(name);
+		err = bpf_btf_get_info_by_fd(fd, &info, &len);
+		if (err) {
+			err = -errno;
+			goto err_out;
+		}
+		/* find target module btf */
+		if (!strcmp(name, module))
+			break;
+
+		close(fd);
+	}
+
+	return fd;
+err_out:
+	close(fd);
+	return err;
+}
+
+void test_libbpf_probe_kfuncs(void)
+{
+	int ret, kfunc_id, fd;
+	char *kfunc = "bpf_cpumask_create";
+	struct btf *vmlinux_btf = NULL;
+	struct btf *module_btf = NULL;
+
+	vmlinux_btf = btf__parse("/sys/kernel/btf/vmlinux", NULL);
+	if (!ASSERT_OK_PTR(vmlinux_btf, "btf_parse"))
+		return;
+
+	kfunc_id = btf__find_by_name_kind(vmlinux_btf, kfunc, BTF_KIND_FUNC);
+	if (!ASSERT_GT(kfunc_id, 0, kfunc))
+		goto cleanup;
+
+	/* prog BPF_PROG_TYPE_SYSCALL supports kfunc bpf_cpumask_create */
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_SYSCALL, kfunc_id, 0, NULL);
+	if (!ASSERT_EQ(ret, 1, "kfunc in vmlinux support"))
+		goto cleanup;
+
+	/* prog BPF_PROG_TYPE_KPROBE does not support kfunc bpf_cpumask_create */
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_KPROBE, kfunc_id, 0, NULL);
+	if (!ASSERT_EQ(ret, 0, "kfunc in vmlinux not suuport"))
+		goto cleanup;
+
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_KPROBE, -1, 0, NULL);
+	if (!ASSERT_EQ(ret, 0, "invalid kfunc id:-1"))
+		goto cleanup;
+
+	ret = libbpf_probe_bpf_kfunc(100000, kfunc_id, 0, NULL);
+	if (!ASSERT_ERR(ret, "invalid prog type:100000"))
+		goto cleanup;
+
+	if (!env.has_testmod)
+		goto cleanup;
+
+	module_btf = btf__load_module_btf("bpf_testmod", vmlinux_btf);
+	if (!ASSERT_OK_PTR(module_btf, "load module BTF"))
+		goto cleanup;
+
+	kfunc_id = btf__find_by_name(module_btf, "bpf_kfunc_call_test1");
+	if (!ASSERT_GT(kfunc_id, 0, "func not found"))
+		goto cleanup;
+
+	fd = module_btf_fd("bpf_testmod");
+	if (!ASSERT_GT(fd, 0, "module btf fd"))
+		goto cleanup;
+
+	/* prog BPF_PROG_TYPE_SYSCALL supports kfunc bpf_kfunc_call_test1 in bpf_testmod */
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_SYSCALL, kfunc_id, fd, NULL);
+	if (!ASSERT_EQ(ret, 1, "kfunc in module btf support"))
+		goto cleanup_fd;
+
+	/* prog BPF_PROG_TYPE_KPROBE does not support kfunc bpf_kfunc_call_test1
+	 * in bpf_testmod
+	 */
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_KPROBE, kfunc_id, fd, NULL);
+	if (!ASSERT_EQ(ret, 0, "kfunc in module btf not support"))
+		goto cleanup_fd;
+
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_SYSCALL, -1, fd, NULL);
+	if (!ASSERT_EQ(ret, 0, "invalid kfunc id in module btf"))
+		goto cleanup_fd;
+
+	ret = libbpf_probe_bpf_kfunc(BPF_PROG_TYPE_SYSCALL, kfunc_id, 100, NULL);
+	ASSERT_EQ(ret, 0, "invalid btf fd in module btf");
+
+cleanup_fd:
+	close(fd);
+cleanup:
+	btf__free(vmlinux_btf);
+	btf__free(module_btf);
+}